It is specifically said in the rules that vampires have very little to do with Umbra, with the rare exception of Giovanni, who can summon wraiths for the Shadowlands and rare Kolduns who can summon minor ethereal entities and interact with them.
It is also reiterated in MtA, that the Embrace effectively performs Gilgul on subject's Avatar, destroying it.
Furthermore, I haven't yet seen any power innate to vampires that could enable them to traverse the Gauntlet.
However, I am not entirely sure, whether vampires can or cannot enter Umbra. Wraiths are Avatar-less as well and they can pass the Gauntlet (or be forcibly dragged through it). Some of my friends argued, that vampires are technically soulless (hard to establish if that's true) and they should be treated like objects – capable of being passed, but unable to manipulate Etherea or travel on their own. Other arguments I heard is that Avatar-less creatures cannot pass, unless they are ethereal in the first place (with Weres being treated as having a common group Avatar – Gaia) or that since they leave no mark in Umbra, they cannot exist there at all.
However, I find it quite perplexing, with a specific situation where a Dreamspeaker mage wanted to lead a Tremere elder through Umbra, causing a massive argument whether it should be possible or not and what are the implications for the vampire and his possibilities when in Umbra. Could you please clear it for me? I'm not looking for RAW verdict, but rather a RAI interpretation.